This paper presents the behaviour of a new metro coach on a newly built track in Kolkata, India. Oscillation trials were conducted using LVDT sensors at different locations to monitor primary and secondary springs compression. Multibody dynamics model is built with actual parameters of coach and track in SIMPACK. The behaviour of the vehicle for given track with elevation and curvature changes has been studied. Vehicle performance has been evaluated based on safety, running behaviour and track fatigue mentioned in UIC 518. Results of primary and secondary spring compressions obtained from field trials and multibody dynamics model have been compared. Coach lateral and vertical acceleration, bogie lateral acceleration, static load at rail wheel contact and derailment coefficient obtained from the multibody dynamics model are discussed. Obtained results were within permission values. Scope of this paper lies in studying the vehicle performance in connection to safety and running behaviour of newly introduced metro in Kolkata.

Conventional problem solving is a time-honored and accepted methodology for solving many problems we encounter in our daily home and work lives. Thought processes can be linear (like a programmer) or non-linear and still use conventional problem solving skills. Conventional problem solving begins with a statement of the problem, accumulation of data, analysis of data and proposals of solutions to the problem, then testing of the hypotheses. Non-conventional problem solving often skips some of these steps, beginning with a statement of the problem and ending with possible solutions. The tools of conventional problem solving include “critical thinking”, Fool-proofing, “thinking outside the box” and Statistical techniques. Consider the first of our ancestors to figure out that harnessing fire would provide security from large predators, make food safer and easier to eat and make tools such as fire hardened tips on spears. Did all these inventions occur in one moment of genius, or did they take innumerable years to accomplish? Sometime in this process of non-conventional thinking our ancestors brought forth a new technology which ensured the survival of our species. So, how does non-conventional problem solving work? When current theory does not appear to work, then we look to the margins of our science to see if current theory continues to be ineffective. Most theories fail in the margins of the science. A classic example of conventional science failing in the margins is the general and special theory of relativity. Non-conventional problem solving offers greater opportunity for revolutionary rather than incremental, or evolutionary advancements to our science. Other examples are included in this paper. Two wheel related problems are also presented using non-conventional problem solving techniques to provide alternative solutions.

A series of specially designed granular material pressure cells were precisely positioned directly below the rail at the tie/ballast interface to measure typical interfacial pressures exerted by revenue freight trains. These vertical pressures were compared to the recorded wheel/rail nominal and peak forces for the same trains traversing nearby mainline wheel impact load detectors (WILDs). The cells were imbedded within the bottom of new wood ties so that the surfaces of the pressure cells were even with the bottoms of the ties and the underlying ballast. The cells were inserted below consecutive rail seats of one rail to record pressures for a complete wheel rotation. The stability and tightness of the ballast support influenced the magnitudes and consistencies of the recorded ballast pressures. Considerable effort was required to provide consistent ballast conditions for the instrumented ties and adjacent undisturbed transition ties. Norfolk Southern (NS) crews surfaced and tamped through the test section and adjacent approach ties. This effort along with normal accruing train traffic subsequently resulted in reasonably consistent pressure measurements throughout the test section. The impact ratio (impact factor) and peak force values recorded by the WILDs compared favorably with the resulting magnitudes of the transferred pressures at the tie/ballast interface. High peak force and high impact ratio WILD readings indicate the presence of wheel imperfections that increase nominal forces at the rail/wheel interface. The resulting increased dynamic impact forces can contribute to higher degradation rates for the track component materials and more rapid degradation rates of the track geometry. The paper contains comparative WILD force measurements and tie/ballast interfacial pressure measurements for loaded and empty trains. Typical tie/ballast pressures for locomotives and loaded freight cars ranges from 20 to 30 psi (140 to 210 kPa) for smooth wheels producing negligible impacts. The effect of increased wheel/rail impacts and peak force values on the correspondingly transmitted pressures at the tie/ballast interface is significant, with increased pressures of several orders of magnitude compared to nominal impact forces from wheels.

The vast majority of railway construction and maintenance machines is powered by compression-ignition combustion engines. The tendency of introducing stringent standard emission regulations for these prime movers, e.g. TIER 4, forces the migration toward downsized units. Additionally, the high price reached by diesel fuel in the last decades demands reductions of the machines’ energy consumption in order to maintain the customers’ operating costs competitive. Both targets can be achieved by implementing efficient hybrid hydraulic displacement-controlled architectures that reduce pollutants emissions and benefit fuel saving without affecting the system’s productivity. For these reasons, this research paper aims at investigating the potentials of a series-parallel hybrid architecture grounded on secondary controlled hydraulic motors and potentially suitable for any railway construction and maintenance machinery. The results demonstrate that the rated engine power can be reduced by at least 35% in the reference application by applying such a propulsion system. Specifically, the high-fidelity multi-domain dynamic model created for sizing, analyzing, and controlling this displacement-controlled layout is addressed. Special focus is dedicated to the rail/wheel interface confirming that the proposed control strategy maintain the slip/spin of the wheels within the desired limits.

Since the adoption of 286,000 lb gross rail load (286K GRL) car service, an increase in wheel thermal damage and shelling has been observed. This is attributed to the increased braking horsepower in 286K GRL service as compared to the 263K GRL service environment. This study investigated possible designs and methods of braking that could lead to reduced heat input to the tread of freight car wheels in order to mitigate this damage and reduce its occurrence to a level closer to that seen with 263K GRL car service. Fifteen potential concepts to lower the thermal input to wheels and/or accelerate heat removal from the tread were identified and evaluated using the following engineering categories: simplicity of design, maintenance requirements, weight considerations, material and manufacturing costs, controllability of braking effort, and market acceptability. Five final concepts — axle-mounted disc, cheek disc, wheel rim, axle-mounted drum, and high convection coating — were developed through preliminary design and thermal analysis to confirm their effectiveness in meeting the objectives. Four concepts for alternative braking methods — axle-mounted disc brakes, cheek disc brakes, wheel rim clasp brakes, and axle-mounted drum brakes — were analyzed in considerable detail. Of the four concepts presented, the first three appear to be feasible and would be potential candidates for further detailed investigations/evaluation. It is shown that as the demand on railway wheels to withstand increased mechanical and thermal loads grows, there are viable braking enhancements that can help manage the stress state in freight car wheels.

Brake heating of Railroad Wheels has been known to accelerate shelling, soften the wheel tread and contribute to stress reversal which is a requisite for generating thermal cracks. The effect brake heating has on shakedown has been investigated to a lesser extent, yet even here brake heating can be very important. This research combines field investigations and laboratory work in an attempt to quantify the thermal effects on wheel performance, especially as it relates to sub-surface shelling, microstructural changes and hardening mechanisms. Cyclic tensile tests were conducted at three temperatures to show the relationship between deformation at elevated temperatures and hardening response. Ductility measurements from both monotonic and cyclic tests were used to estimate residual stresses.

Railway wheels and rails do not achieve full wear life expectancy due to the combination of wear, plastic deformation, and surface, subsurface, and deep subsurface cracks. Sixty-seven percent of wheel replacement and maintenance in North America is associated with tread damage [1]. Spalling and shelling are the two major types of wheel tread damage observed in railroad operations. Spalling and slid flat defects occur due to skidded or sliding wheels caused by, in general, unreleased brakes. Tread shelling (surface or shallow subsurface fatigue) occurs due to cyclic normal and traction loads that can generate rolling contact fatigue (RCF). Shelling comprises about half of tread damage related wheel replacement and maintenance. The annual problem size associated with wheel tread RCF is estimated to be in the tens of millions of dollars. The total cost includes maintenance, replacement, train delays and fuel consumption. To study the conditions under which RCF damage accumulates, a 36-ton axle load aluminum body coal car was instrumented with a high accuracy instrumented wheelset (IWS), an unmanned data acquisition (UDAC) system, and a GPS receiver. This railcar was sent to coal service between a coal mine and power plant, and traveled approximately 1,300 miles in the fully loaded condition on each trip. Longitudinal, lateral, and vertical wheel-rail forces were recorded continuously during four loaded trips over the same route using the same railcar and instrumentation. The first two trips were conducted with non-steering 3-piece trucks and the last two trips were conducted with passive steering M-976 compliant trucks to allow comparison of the wheel load environment and RCF accumulation between the truck types. RCF initiation predictions were made using “Shakedown Theory” [2]. Conducting two trips with each set of trucks allowed for analysis of the effects of imbalance speed conditions (cant deficiency or excess cant) at some curves on which the operating speeds varied significantly between trips.

As transportation costs rise, rail stock material improvements are critical to improving efficiency, durability, and performance. Steel wheels have been a consistent part of rail equipment, but it may be time to assess potential other alloys and materials in anticipation of future demands. Strength requirements are steadily increasing with rail car capacity, while weight savings in equipment can reduce fuel costs and/or increase carrying capacity. Herein, the current requirements for railroad wheels are discussed and compared with experimental evaluation of a potential alternative material, austempered ductile iron (ADI). ADI is an attractive wheel material because of its higher strength-to-weight ratio (as compared to steel) and its wear resistance. ADI castings are also typically cheaper to produce than steel. While ADI can meet or exceed the strength of steel components, it is also comparable in ductility and impact strength, so conversion to ADI does not bring additional risk of brittle fracture, as is commonly the case when achieving higher strengths. There are challenges with its implementation, however. AAR certification of new materials is costly and time consuming, so adoption is unlikely until there is a very compelling business case. Heat produced during on-tread braking has the potential to damage the heat-treated structure of ADI. The regular exchange of cars across different sections of track and therefore different managing companies requires that new wheel materials be fully backwards compatible, so alterations in design are severely limited. This paper will take initial steps toward assessing the potential of ADI railroad wheels by investigating the performance of ADI at elevated temperatures, and comparing the results to measured and simulated wheel temperatures.

Plastic deformations alter the mechanical properties of many metals and alloys. Class C and Class D wheel steels such as are used in North American freight car service are particularly affected by plastic deformations occurring during rolling contact between the wheel tread and rail head. This investigation determines the effect plastic deformations have on the mechanical properties of Class C and D wheel steels and how those changes could relate to shakedown theory. The effect of temperature is also discussed.

On-tread braking generates high heat and often results in temperatures on the tread surface in excess of 400C (750F). Temperatures this high result in rapid oxidation of the tread surface. High temperature oxidation for steel generally follows a parabolic rate law: the time to generate a given weight or thickness of an oxide layer increases proportionately to the square of the weight or thickness of that oxide layer. The decrease in the rate of generation of new scale thickness results from the longer time it takes for oxygen to diffuse through an increasingly thicker layer of oxide. However, wheel/rail contact and abrasive action from the brake pad often erodes the oxide layer as it forms, accelerating the rate of formation of the oxide. Further, as the oxide forms, cold worked tread material from rolling contact forces is removed thereby reducing the beneficial residual stresses and higher hardness layer that may have protected the tread surface from further plastic deformation. Environmental factors may also aggravate oxidation losses sufficiently to make it a primary rather than a secondary cause of wear. High temperature oxidation can contribute to an accelerated rate of shelling, which can result from oxide forming within tread cracks. Tensile stresses at the crack tip are caused by expansion when the oxide forms. Compressive stresses in the oxide are usually minimal, as expansion is not constrained in the scale growth direction. Volume constraints within a crack when the oxide forms generates compressive stresses in the newly formed oxide, which results in wedging forces at the crack tip. Oxidation of the tread surface may permit debris to adhere to the tread surface creating a defect called “built-up tread”. Although built-up tread defects require other factors in order to become a problem, oxidation of the tread surface appears to be an initiating mechanism. Results from experimentation and Finite Element Analyses are used to support this work.

The aim of the paper is to classify restraining rail, discuss the advantages and disadvantages of each type of restraining rail, derive the formula to determine the flangeway gap, and finally, to suggest a type of restraining rail for use. Three types of restraining rail are classified as: 1. Active restraining rail: Defined as the restraining rail that reduces the angle of attack (AOA) by more than 50%. 2. Semi-active restraining rail: Defined as the restraining rail that reduces the AOA by 50% or less, preferably between 40% ∼ 50%. 3. Passive restraining rail: Defined as the restraining rail that does not reduce the AOA. In other words, it plays a passive role in steering the wheel. A design procedure is established to estimate the flangeway gap. The advantages and disadvantages of each type of restraining rail are discussed from design, maintenance, and functional points of view. The issue of optimization of the rail/wheel profile is also discussed in context with the presence of restraining rail. One component of the flangeway gap is the space required for the angularity of the wheel. 2D CAD drawings are not efficient for this purpose, as the drawings cannot consider the AOA and the height of restraining rail on top of the rail level. In this context, Nytram plot is a solution; however, the plot needs a number of sectional drawings at gauge point level, rail level, and the top-of-restraining-rail level from the 3D drawing. A mathematical model that counts both the AOA and the height of restraining rail from the top of the rail level is developed here to capture the essence of the Nytram plot, and thereby to assess the space required for the angularity of the wheel. Finally, a semi-active restraining rail, with a formula for flangeway gap, is suggested for use. Being less elaborate and less time consuming, the formula is easier and quicker than the Nytram plot to estimate flangeway gap. Moreover, one can quickly assess the effect of wheel size, the height of the restraining rail from the top of rail, and the radius of the curve on the flangeway gap.

Recent work using x-ray diffraction techniques has shown that the axial residual stress pattern within the railroad wheel rim is significantly different for as-manufactured AAR Class C wheels vs. AAR Class C wheels that have failed due to a vertical split rim (VSR), and non-failed AAR Class C wheels that have been operating in service. VSRs almost always begin at areas of tread damage, resulting from shelling or spalling, and cracking propagates into the rim section under load. At the locations tested, the as-manufactured wheels have a relatively “flat” axial residual stress profile, compressive but near neutral, caused by the rim quenching operation, while wheels that have been in service have a layer of high axial compressive stress at the tread surface, and a balancing zone of axial tensile stress underneath. The magnitude and direction of this tensile stress is consistent with the crack propagation of a VSR failure. When cracks from the tread surface propagate into this sub-surface axial tensile zone, a VSR can occur under sufficient additional service loading, such as loads caused by in-service wheel/rail impacts from tread damage. Further, softer Class U wheels, removed from service and tested, were found to have a balancing axial tensile stress layer that is deeper below the tread surface than that found in used Class C wheels. This paper describes further efforts to characterize the axial residual stress present in failed VSR and used Class C wheels. Axial residual stress results are obtained near the initiation point of several VSR wheels using x-ray diffraction. Sub-surface axial residual stress patterns are also determined at points of high out-of-roundness for a group of wheels that were tested for TIR (total indicated runout) on the tread surface. Residual stress data and a photo are presented for a wheel rim slice containing a second VSR crack. Additionally, wheel rim ultrasonic testing data, collected by the wheel manufacturer when the wheels were new, are discussed for wheels that have failed due to VSRs and these data are compared to ultrasonic data for non-VSR wheels. Chemistry data are also compared. These data show that the driving force for VSRs is axial residual tensile stress, not a material cleanliness issue.

Classic shelling of a railway wheel begins with crack initiation resulting from wheel rail interactions. This investigation shows the complex relationships that occur between contact stress, cold work, residual stresses, and temperatures from brake heating and non-metallic inclusion types which can lead to the formation of shelling cracks. Our investigation also includes an explanation of how these interactions affect mechanical properties such as yield strength, elastic modulus, and ductility. In turn, mechanical property changes also affect how cold work and its associated residual stresses develop under cyclic loading. Destructive testing and Finite Element Analyses were used in support of this work.

Consistent process control of wheel hardness and residual stresses developed during heat treatment are particularly important considerations for service life and safety of railway wheels. This paper details the process controls strategically located throughout an integrated, fully automated heat treatment system that can heat treat up to 65 railway wheels per hour. New, innovative technology such as in-line temperature measurements that control key process steps, uniform wheel heating and cooling, and quench water temperature and pressure control have resulted in wheel hardness and residual stress values with less statistical variation than older, traditional heat treat methods. Automatic serial number tracking and temperature measurement allow for statistical analysis of heat treat processes. Two years after the commissioning of this $18M facility, the quality and productivity benefits realized are discussed.

Vertical split rim cracking, rapid unstable propagation of a sub-surface crack parallel to the front rim face, is one of the dominant railroad wheel failure types observed in North America. Wheel impact load is believed to be a trigger for this unstable crack growth. This rapid crack growth rate depends on several factors, such as wheel geometry (wheel diameter and rim thickness), load magnitude, load location, residual stresses in the rim, worn tread profile, and material defects in the rim (size, shape, location, and orientation). This paper investigates the effect of these parameters on vertical split rim cracking, using finite element analysis and fracture mechanics. Vertical split rim cracking is modeled using a three-dimensional, multiresolution, elastic-plastic finite element analysis. Material defects are modeled as mathematically sharp cracks. Wheel impacts are simulated by applying a high axle load on the tread surface. The residual stress and wheel wear effects are also included in modeling vertical split rim cracking.

A target-oriented method for the design of railway wheel profiles is presented. The target chosen is the rolling radii difference function which plays an important role in the dynamics of railway vehicles especially for high speed performances. A computer program based on this method has also been developed and is validated by way of examples in which wheel profiles LMA, S1002G and XP55 are investigated.

Residual stresses in railroad wheel rims significantly affect the wheel failure life; therefore, it is important to consider residual stresses for wheel failure analysis. In this paper, an advanced computational methodology is developed to estimate residual stresses developed during both the manufacturing process and under service conditions. To estimate the residual stresses in the wheel, three-dimensional decoupled thermal-structural analyses are performed. To simulate the manufacturing process, thermal analysis is performed with convection boundary conditions on the wheel surfaces. The temperature distributions obtained from this thermal analysis are input as loads for structural analysis. The results represent as-manufactured residual stresses. To simulate the thermal brake loading under service conditions, thermal analysis is performed using a heat flux boundary condition on the tread surface. Structural analysis is performed, including the estimated as-manufactured residual stress as initial stress, and using the temperature distributions obtained from thermal analysis of the on-tread braking. The resultant stresses represent the complex combination of residual stresses developed during both the manufacturing process and on-tread braking. The computed results are compared with the experimental data obtained at TTCI and the values reported in the literature.

Catastrophic bearing failure is a major concern for the railroad industry because it can lead to costly train stoppages and even derailments. Excessive heat buildup within the bearing is one of the main factors that can warn of impending failure. A question is often raised regarding the transfer of heat from a wheel during braking and whether this can lead to false setouts. Therefore, this work was motivated by the need to understand and quantify the heat transfer paths to the tapered roller bearing within the railroad wheel assembly when wheel heating occurs. A series of experiments and finite element (FE) analyses were conducted in order to identify the different heat transfer mechanisms, with emphasis on radiation. The experimental setup consisted of a train axle with two wheels and bearings pressed onto their respective journals. One of the wheels was heated using an electric tape placed around the outside of the rim. A total of 32 thermocouples scattered throughout the heated wheel, the axle, and the bearing circumference measured the temperature distribution within the assembly. In order to quantify the heat radiated to the bearing, a second set of experiments was developed; these included, in addition to the axle and the wheel pair, a parabolic reflector that blocked body-to-body radiation to the bearing. The appropriate boundary conditions including ambient temperature, emissivity, and convection coefficient estimates were measured or calculated from the aforementioned experiments. The FE thermal analysis of the wheel assembly was performed using the ALGOR™ software. Experimental temperature data along the radius of the heated wheel, the bearing circumference, and at selected locations on the axle were compared to the results of the FE model to verify its accuracy. The results indicate that the effect of thermal radiation from a hot wheel on the cup temperature of the adjacent bearing is minimal when the wheel tread temperature is at 135°C (275°F), and does not exceed 17°C (31°F) when the wheel tread is at 315°C (600°F).

Reduced friction with top of the rail friction modifiers continues to be investigated for improved energy efficiency and reduction in lateral forces between railroad car wheels and the rail. Another benefit often not considered is the potential reduction in wear of both the wheel and the rail surfaces. This paper details the results of fundamental laboratory test work to compare dry contact condition with one where a “friction modifier” has been applied, to define the difference in the surface deterioration and wear. The basics of this wear testing are described, along with information on the materials used for the testing. The results show a very significant difference in friction coefficients and the wear characteristics, suggesting substantial benefit potential in both reduced rail wear and wheel tread wear. Selected wheel wear tests are discussed and historical wheel wear information is provided. Wheel life data for two North American coal freight car fleets are reviewed to point out the average mileage of wheels in service. The potential for increasing wheel wear life, and therefore potential cost savings, is highlighted. Finally, recommendations for future work are offered.

This paper describes a major capital project that was recently completed at a North American wrought railroad wheel manufacturing facility. The overall goals and concept of the project are outlined. Upgrades and improvements to band saws, the 10,000 ton forging press, rolling mill, and associated hydraulic systems, are described with emphasis on improvements in process speed. Installation of new wheel handling robots, which replaced an additional number of older, less robust wheel handling robots, is reviewed. Further, a new in-line wheel heat treating process, which provides for rim quenching and tempering of the wheel shortly after the forging and rolling process is completed, is described in detail. The new computer-controlled heat treating process features a rotary heating furnace to austenitize the wheels, several rim spray stations for quenching, a slot-in-the roof tempering furnace, controlled cooling operations, and automated Brinell testing. Important equipment maintenance concerns that were addressed are also reviewed. Finite element analysis (FEA) results for the new wheel heat treating process are discussed, along with other process considerations.